A common vehicle accident scenario is for a first vehicle at the end of a traffic jam, or at the end of a queue waiting at an intersection, to be hit from behind and pushed into a second vehicle in front of the first vehicle. For certain events, even low-g impacts, a driver can be startled and/or or physically move such that the driver's foot slips off the brake pedal and hits an accelerator pedal. This problem can occur in any vehicle, but may be particularly likely in cars having a small distance between pedals. Additionally or alternatively, a driver may have his or her foot off the brake pedal, hovering above the accelerator pedal such that an impact force causes a driver's foot to push the accelerator pedal down.
The effect of such accident behavior, even in low-g impacts, can have significant consequences. For example, a change in state when an accelerator pedal is inadvertently depressed after an impact can cause a release from a zero-movement or low-movement state to a higher-movement state, which can then cause a vehicle that was initially impacted to in turn impact a next vehicle in a queue, or even worse, travel into an intersection when the impacted vehicle does not have the right-away. At even very low speed impacts, vehicles can endure thousands of dollars' worth of damage, or in the latter case vehicle occupants can sustain serious injuries.
Existing systems address only high-g impacts. For example, when a high-g impact is detected, e.g., an impact at an acceleration of 3-4 g (hereinafter described as a g-force level of 3-4), a fuel cut-off system can cut the fuel flow to the engine to prevent forward movement of a vehicle. Such systems may assume, for example, constant acceleration, where vehicle acceleration=(vehicle velocity at time n−vehicle velocity at time zero)/time. At an impact having lower force, e.g., an acceleration of 1-3 g, (i.e., a g-force level of 1-3), where engine fuel is not cut off, and when a driver inadvertently depresses a brake or accelerator pedal, systems are lacking to prevent undesired forward movement of a vehicle. (A “g-force” is generally defined as 9.81 m/s2 or 32.2 ft/sec2.)
A g-force in the range of 1-3 is nonetheless sufficient to startle a driver and/or cause a driver to lose footing on vehicle pedals. Accelerations or g-forces in this range are generally low enough energy such that typical injuries are not serious. However, additional vehicle movement can increase the likelihood and severity of rear impact-induced injuries, or other injuries if the vehicle is pushed into an intersection.